Quickly Capture Theory And Technology Research. Spread Spectrum Communication System

In this paper, A new approach to Pseudo Noise (PN) code acquisition for a Code Division Multiple Access(CDMA) direct sequence spread spectrum system is presented and analyzed. A recirculation loop is used to improve probability of synchro cell detection P_D and probability of false alarm P_fa simultaneously.so , the new acquisition system can reduce the mean acquisition time and the variance of the acquisition time.Performance analysis of these algorithms has shown that the average acquisition time and its variance can be reduced up to 25 and 60 times, respectively, at SNR=-10dB. But if the SNR is increased over 10 dB the improvement vanishes.These algorithms make CDMA techniques feasible for direct communication between LEO satellite and small ground-based user terminals(handsets).Assuming in the white gauss noise channel,the average acquisition time and its variance of the single dwell acquisition is derived by using method of flow graph and direct probability.And, the new acquisition system based on a recirculation loop is analyzed using method of direct probability.The average acquisition time and its variance has improved.Results of simulations are shown that it is viable.Because the acquisition is rapid and the equipments is little,the new acquisition system is applied in direct sequence spread spectrum system to improved communication.